The records and manuscripts of the Groton Province contains correspondence, publications, notes, minutes, and abstracts, newspaper clippings, photographs, records, and annals produced by the Sisters from before their establishment in North America until the consolidation of the Groton and Fall River Provinces in 1999. The contents of this collection reflect the activity, ministry, and community trends within the Sisters in the 20th century, as well as their relations with other Provinces, mission work overseas, and the broader expansion and decline of Catholic education between 1945 and 1999, as well as changes and experimentation among religious orders pre- and post-Vatican II. The collection is arranged per the Mollette system, and reflects the organization of the community and its activities, and is divided into series primarily on a subject basis.

Series A covers foundation, including the literal foundation of the Province, writings regarding Abbé Debrabant and the early history of the congregation, and constitutions of the Province as a whole. It is the broadest series in timescale, as it contains pre-founding documents from 19th-century France and Belgium, as well as all revisions of the governing structure of the Sisters of this Province up until the merger in 1999.

Series D covers relations with ecclesiastical authorities, individuals and organizations within the Roman Catholic Church but outside of the congregation and the sphere of women religious. These include the Archdiocese of Boston, the Dioceses of Providence and Fall River, and the Holy See in Rome, among others.

Series E covers relations with other organizations of women religious, such as nuns, lay sisters, and associates of other orders. This series primarily focuses on relations with the Leadership Conference of Women Religious.

Series F covers corporation, the legal structuring of the Province and its activities.

Series G covers general administration, the day-to-day operation and communication of the Holy Union Sisters as a whole, and the communications and involvement of the Groton Province with the overall administration of the Holy Union congregation. These materials include reports, circulars, annals, and newsletters from the General Council, as well as directories, Provincial assemblies, renewal and Province-wide development programs, and internal newsletters and publications directed to the Sisters.

Series H covers relations with other individual provinces, within the Holy Union Sisters, including correspondence between leadership, grants and mission planning, and Provincial newsletters. These other provinces within the congregation include Fall River (see Fall River Province finding aid), Anglo-Hibernia/Tanzania, Cameroon, Argentina, Franco-Belgium, and Haiti. This section also covers communities within the congregation, such as individual convents, and their annals and correspondence. These communities include Our Lady of Pity (Cambridge, MA), Sacred Heart (North Attleboro, MA), and Rose Hawthorne (Concord, MA), among others. Note that this series covers these communities in their activities as convents, not the operation of schools with which they may have been affiliated.

Series J covers personnel, and includes personal information concerning individual Sisters both living and deceased, in addition to writings, theses, and artworks produced by Sisters and kept by the community. Subseries 1J, concerning pre-novitiate evaluations and subseries [x]J, concerning former Sisters, are currently restricted. Specific materials kept in this series include records of clothings and professions, dispensations and departures, and educational records of individual Sisters.

Series K covers formation, the process of admittance and profession into the order, as well as the ongoing personal and professional development of individual Sisters and the community as a whole. This series includes information on entrance and profession ceremonies, vocations, discernment, retreats and sabbaticals, and conferences and workshops.

Series L covers spirituality, the structured worship, liturgy, theology, and devotion of the community and its members.

Series M covers ministry, the activity of the Sisters outside of the congregation as directed by their charism. For the Holy Union Sisters, this ministry is primarily education, and this series contains most information, records, and publications related to the numerous schools operated or staffed by the Sisters of this Province, such as St. Michael's, Bishop Cassidy, St. Cecilia, Rose Hawthorne, the Country Day School, and St. Mary.

Series N covers associates, lay individuals of both sexes affiliated to the congregation as groups of organized supporters, and their activities and organization.

Series P covers publications, the materials produced for circulation and consumption outside of the congregation. These include newsletters, announcements, jubilees, development and aid, and promotional materials for the 1986 centennial of the Holy Union Sisters in North America. This series also includes materials covering discussion of building projects and financial aid, where those matters required input from the broader community.

Series T and Q cover temporalities, the financial and real estate holdings of the community and their management. This series includes ledgers, accounting books, deeds and loan documentation, invoices, assessments, and fundraising reports.